Hypothalamus and pituitary gland.ppt by ZubairLatif


Hypothalamus and pituitary gland.ppt

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									Hypothalamus & Pituitary Gland

           Zubair Latif
                Endocrine Glands
•   Hypothalamus
•   Pituitary
•   Thyroid gland
•   Parathyroid glands
•   Adrenal Glands
•   Pancreas
•   Gonads
•   Pineal gland
•   Thymus
•   others

    Endocrine Gland Functions
• Secrete hormones into blood
  – Regulatory effect on metabolic functions
  – Hormones exert effects at many sites
     • Often at distance from origin
• Steroid hormones
  – Manufactured from cholesterol
     • Cortisol, aldosterone, estrogen, progesterone, and

• Nonsteroid hormones
  – Synthesized from amino acids
     • Insulin, parathyroid hormone, and others
                Hormone Receptors
• Hormones categorized as:
   – Proteins
   – Polypeptides
   – Derivatives of amino acids

• Hormone may affect specific
  organ or tissue or have
  general effect on entire body
    Regulation of Hormone Secretion

Hormones operate within feedback systems to
 maintain internal environment
   Regulation of Hormone Secretion
Negative feedback
  Most common
  Increase in serum level
    of hormone or
    related substance
    suppresses further
    hormone output
  Production is stimulated
    when serum levels
– Regulates ANS,
  feeding/satiety, thirst,
  body temperature, etc.
– Hormones related to
  these functions
   • “Releasing hormones”
   • Axonal transport to
     posterior lobe

  Hypophysiotropic hormones
– Thyrotropin-releasing hormone (TRH)
– Corticotropin-releasing hormone (CRH)
– Gonadotropin-releasing hormone (GnRH)
– Growth hormone-releasing hormone (GHRH)
– Growth hormone-inhibiting hormone (GHIH)
– Prolactin-releasing factor (PRF)
– Prolactin-inhibitn hormone (PIH)
Localization of Neurons Producing Releasing

•   GnRH: preoptic area, arcuate nucleus
•   CRF: paraventricular nucleus
•   GHRH: arcuate nucleus
•   somatostatin: anterior periventricular region
•   TRH: paraventricular nucleus
•   PRIF: arcuate nucleus
     Transportation of Releasing Factors to the
                 Anterior Pituitary

Neurons send projections from their
   location in the hypothalamus to the
   median eminence.
At median eminence, neurons secrete
   releasing factors into a capillary bed
Blood flows through the pituitary
   portal vein, to a capillary bed in the
   anterior pituitary
Hormone is released into general
            Controls of Releasing Factors

• The neurons which produce release factors are
  themselves usually controlled by other neurons, which
  release neurotransmitters.
                                               neuron controlling
                                        neuron producing releasing factor

                     neuron producing
                     releasing factor                           feedback

                      median eminence
     capillary bed
Feedback Control of Hormone Release from
          the Anterior Pituitary
                                                     neuron controlling
                                              neuron producing releasing factor

                          neuron producing
                          releasing factor                            feedback

                            median eminence
   capillary bed
               releasing factor

anterior pituitary cell

“Releasing” hormones
  regulate anterior Pituitary
• Synthesizes
  hormones in cell bodies
• Transports hormones
  down the axon and
  stored in the nerve
• Secretion of hormones
  is in pulses

• Hypothalamic cell
  bodies synthesize
  oxytocin and ADH
• Axonal transport to
  posterior pituitary
• Release from
  posterior pituitary

Pituitary Gland
              Growth Hormone
• Increased rate of protein
  synthesis in most cells of
• Increased mobilization of
• fatty acids from adipose
  tissue, increased free
  fatty acids in the blood,
  and increased use of
  fatty acids for energy
• Decreased rate of
  glucose utilization
  throughout the body
  GH & Carbohydrate Metabolism
• Decreased glucose uptake in tissues such as
  skeletal muscle,
• Increased glucose production by liver
• Increased insulin secretion (insulin resistance
  leading to “Pituitary diabetes”
• Stimulate Somatmedins from liver (IGF-1)
• Mobilization of fats is so great that large
  quantities of acetoacetic acid are formed by liver
  causing ketosis
• The pygmies of Africa have a congenital
  inability to synthesize significant amounts of
  somatomedin C.
• Therefore, high concentration of GH, but low
  IGF-I . this apparently accounts for the small
  stature of these people. Some other dwarfs
  (e.g., the Lévi-Lorain dwarf) also have this
Regulation of GH
Diets & GH
         Abnormalities of Growth
           Hormone Secretion
Panhypopituitarism (congenital or acquired that
  may occur suddenly or slowly)
Congenital in childhood, A child who has reached
  the age of 10 years may look like a 4-5 years child
  aged 4 to 5 years,
Or 20 years old may have the bodily development
  of a child aged 7 to 10 years
Panhypopituitary dwarfism does not pass through
  puberty and never secretes sufficient quantities
  of gonadotropic hormones to develop adult
  sexual functions.
     Panhypopituitarism in Adult
Tumorous (craniopharyngiomas or chromophobe
  tumors), may compress the pituitary gland until
  the functioning
Anterior pituitary cells are totally or almost totally
  destroyed causing
• Hypothyroidism,
• Depressed production of glucocorticoids by
  adrenal glands
• Suppressed secretion of the gonadotropic
  hormones so that sexual are lost.
Somatrotrops become excessively
Giant ordinarily has hyperglycemia,
    and beta-cells are prone to
    degenerate Consequently, in
    about 10% have full-blown
    diabetes mellitus
If after adolescence, that is, after
    the epiphyses of the long bones
    have fused with the shafts—the
    person cannot grow taller, but
    the bones can become thicker
    and soft tissues can continue to
    grow (acromegaly)
 Acromegaly: Signs & Symptoms
• Enlargement of
  cranium & lower jaw
  – Bulging forehead
  – Bulbous nose
  – Thick lips &
    enlarged tongue
Acromegaly: Signs & Symptoms
• Enlargement of hands &
   – May have clubbing
• Enlarged liver, heart &
• Typical large teeth with
  frontal space
Acromegaly: Signs & Symptoms
                • Males impotent, females
                  have amenorrhea

                • Severe headaches are

                • Partial or complete
                  blindness if tumor is
                  causing pressure on the
                  optic nerve
       Posterior Pituitary Gland
Also known as
1. ADH or Vasopressin
2. Oxytocin
ADH is formed primarily
  in supraoptic nuclei,
  whereas oxytocin is
  formed primarily in the
  paraventricular nuclei.
Under ADH, collecting tubules and ducts (V2
  receptors) become permeable to water, due to
  insertion of aquaporins-2
Increase the activity of carrier proteins (Na,K
  2Cl) in thick limb of LH
Increase constriction of arteriols (Vasopressin)
  via V1 receptors
  Factors Affecting ADH Secretion
Stimulatory Factors
Increased serum osmolarity
Decreased ECF volume
Inhibitory Factors
Decreased serum osmolarity
Atrial natriuretic peptide (ANP)
                 Diabetes Insipidus
• Transient or permanent disorder of the posterior
  pituitary causing deficiency of production or
  secretion of ADH (central DI)
• Receptors problems (V1) (nephrogenic DI)
• Characterized by:
   – Excessive thirst – polydipsia
     Excessive output – Polyuria, nocturia

   – Skin dry with poor turgor
   – Loss of weight
   – Light color, low specific gravity of urine
•   Excess ADH causes re-absorption of H2O
•   Extracellular fluid volume expands
•   Plasma osmolality declines
•   GFR increases
•   Na levels decline
•   Characterized by:
    –   Fluid retention
    –   Serum hypoasmolality
    –   Dilutional hyponatremia
    –   Hypochoremia (low serum chloride)
    –   Concentrated urine
1) In a hypophysectomized animal, the duration of labor
   is prolonged,
(2) The amount of oxytocin in the plasma increases
   during labor, especially during the last stage.
(3) Stimulation of the cervix in a pregnant animal elicits
   nervous signals that pass to the hypothalamus and
   cause increased secretion of oxytocin.
Oxytocin also acts on myoepithelial cells that lie outside
   of and form a latticework surrounding the alveoli of the
   nmammary glands (milk letdown or milk ejection)

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